In 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) normal CP (Cyclic Prefix), a slot includes 7 SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols. Transmission mode of ACK/NAK (Acknowledge Character/Negative Acknowledge) is shown in FIG. 1. Herein, [S0, S1, . . . , S6] refers to 7 SC-FDMA symbols of a slot. d refers to ACK/NAK symbol to be transmitted. If there is 1 ACK/NAK bit, d refers to a constellation point of BPSK (Binary Phase Shift Keying). If there are 2 ACK/NAK bits, d refers to a constellation point of QPSK (Quadrature Phase Shift Keying). SC-FDMA symbol [S0, S1, S5, S6] is used for transmitting ACK/NAK d (data). Wd=[Wd(0) Wd(1) Wd(2) Wd(3)] refers to OC (Orthogonal Cover) of ACK/NAK data. In LTE, the value of Wd can be OCd0=[1 1 1 1]; or OCd1=[1 −1 1 −1]; or OCd2=[1−1−1 1]. r refers to pilot signal and is equal to 1. SC-FDMA symbol [S2, S3, S4] is used for transmitting r (pilot frequency). Wr=[Wr(0) Wr(1) Wr(2)] refers to spread spectrum code of pilot frequency.
In 3GPP LTE extended CP, a slot includes 6 SC-FDMA symbols. Transmission mode of ACK/NAK is shown in FIG. 2. Herein, [S0, S1, . . . , S5] refers to 6 SC-FDMA symbols of a slot. d refers to ACK/NAK symbol to be transmitted. If there is 1 ACK/NAK bit, d refers to a constellation point of BPSK. If there are 2 ACK/NAK bits, d refers to a constellation point of QPSK. SC-FDMA symbol [S0, S1, S4, S5] is used for transmitting ACK/NAK d (data). Wd=[Wd(0) Wd(1) Wd(2) Wd(3)] refers to OC of ACK/NAK data. In LTE, the value of Wd can be OCd0=[1 1 1 1]; or OCd2=[1−1−1 1]. r refers to pilot signal and is equal to 1. SC-FDMA symbol [S2, S3] is used for transmitting r (pilot frequency). Wr=[Wr(0) Wr(1) Wr(2)] refers to spread spectrum code of pilot frequency. In LTE, the value of Wr can be OCr0=[1 1]; or OCr2=[1−1]. A subframe is comprised of 2 slots and ACK/NAK is transmitted repeatedly on 2 slots of a subframe as shown in FIG. 2.
In 3GPP LTE, a RB (Resource Block) is comprised of 12 REs (Resource Element) and each RE is 15 kHz in terms of frequency domain. For ACK/NAK transmission, a sequence with length of 12 is transmitted on a RB of a SC-FDMA symbol. 12 sequences generated through different CSs (Cyclic Shift) of this sequence are mutually orthogonal. Therefore, an ACK/NAK channel on a RB is determined by a CS and an OC.
Mapping from ACK/NAK channel n to (CS, OC) in a RB under normal CP for the data and pilot frequency of ACK/NAK respectively is shown in Table 1 and 2. ΔPUCCH refers to the CS spacing used in the same OC. In Table 1 and 2, ΔPUCCH is equal to 2. The number (n) of ACK/NAK channel can be either acquired from a higher layer signalling or from CCE index (Control Channel Element index) of PDCCH (Physical Downlink Control Channel).
TABLE 1Mapping from ACK/NAK Channel n to (CS, OC),data, ΔPUCCH = 2, normal CPOCd0 =OCd1 =OCd2 =CS[1 1 1 1][1 −1 1 −1][1 −1 −1 1]0n = 0n = 121n = 62n = 1n = 133n = 74n = 2n = 145n = 86n = 3n = 157n = 98n = 4n = 169n = 1010n = 5n = 1711n = 11
TABLE 2Mapping from ACK/NAK Channel n to (CS, OC), pilotfrequency, ΔPUCCH = 2, normal CPOCr0 =OCr1 =OCr2 =CS[1 1 1][1 ej2π/3 ej4π/3][1 ej4π/3 ej2π/3]0n = 0n = 121n = 62n = 1n = 133n = 74n = 2n = 145n = 86n = 3n = 157n = 98n = 4n = 169n = 1010n = 5n = 1711n = 11
Mapping from ACK/NAK channel n to (CS, OC) in a RB under extended CP for the data and pilot frequency of ACK/NAK respectively is shown in Table 3 and 4. ΔPUCCH refers to the CS spacing used in the same OC. In Table 3 and 4, ΔPUCCH is equal to 2. The number (n) of ACK/NAK channel can be either acquired from a higher layer signalling or from CCE index (Control Channel Element index) of PDCCH (Physical Downlink Control Channel).
TABLE 3Mapping from ACK/NAK Channel n to (CS, OC),data, ΔPUCCH = 2, extended CPOCd0 =OCd2 =CS[1 1 1 1][1 −1 −1 1]0n = 01n = 62N = 13n = 74N = 25n = 86N = 37n = 98N = 49n = 1010N = 511n = 11
TABLE 4Mapping from ACK/NAK Channel n to (CS, OC), pilotfrequency, ΔPUCCH = 2, extended CPOCr0 =OCr1 =CS[1 1][1 −1]0n = 01n = 62n = 13n = 74n = 25n = 86n = 37n = 98n = 49n = 1010n = 511n = 11
For the present ACK/NAK transmission mode, commonly-used demodulation algorithm can be adopted, which means that channel is estimated firstly according to pilot symbol, and then demodulation result is acquired according to demodulation data symbol acquired during signal estimation. Signal estimation and data demodulation are realized by steps in the above demodulation algorithm with pilot symbol operation as the first step and data symbol operation as the second step. Therefore, it fails to make full use of the correlation between pilot symbol and data symbol, thus gaining poor demodulation performance.